Are there any legal experts who could chime in to help me understand the why of this decision?
If these loans are held by the executive branch, why aren't they allowed to cancel their own loans? Is there really a federal law on the books against this?
Because executive action can be used only when it has been specifically authorized by Congress.
It was authorized by congress, specifically the heroes act. It gave the executive branch the power to "waive or modify loans" in reponse to a national emergency, and cornavirus was declared one. The law passed by congress explicitly gives Biden the power to do this. It'd a terrible ruling by the court. Not to mention the suing parties have no standing to begin with, and the suit never should have even gone forward on that basis in the first place.
There is no national emergency anymore. He should have acted when covid was still a thing, or when he had a democrat congress.